Every day he goes to City Hall, Bill de Blasio will have to face Mike Bloomberg.

Hours before his term was to end, Mayor Bloomberg on Monday put his official portrait on prominent display at City Hall — a stark reminder of his legacy to a successor who has attacked the outgoing administration and threatened to undo many of its policies.

Bloomberg had his portrait unveiled next to the Blue Room, a choice City Hall location, on his next to last day.

It was the first time a mayor’s portrait was hung while he’s still in office.

De Blasio, meanwhile, announced he was going full steam ahead on sweeping changes he promised during his election campaign, including doing away with Central Park’s carriage horses.

“We’re going to get rid of the horse carriages. Period,” he promised.

De Blasio, who has steadily criticized the Bloomberg-backed police stop-and-frisk strategy, also named a new schools chancellor who is expected to roll back key parts of Bloomberg’s education policies.

The mayor took the high road as his final hours in office ticked away and joked about the portrait.

Asked by reporters what his favorite part of the painting was, he replied, “It would be vain if I said the person in it.”

He spoke after signing 22 bills into law to round out his administration, including a ban on foam containers, new regulations on e-cigarettes and the creation of a database to track Hurricane Sandy relief funds.

De Blasio, in Brooklyn, prepared to be sworn in officially at his Park Slope home at one minute after midnight by state Attorney General Eric Schneiderman.

The ceremony was to be private, with de Blasio’s entire block sealed off to prevent access by the press and nonresidents.

On Monday, de Blasio introduced Carmen Farina, his choice to run the city schools, who made clear she had different ideas about how to run the system than the current administration.

“We’re going to have a system where parents are really partners,” Farina said, in an implied attack on Bloomberg.

The outgoing mayor didn’t actually see his portrait until Monday morning, according to aides.

He had talks with people in art circles and the name of artist Jon Friedman came up a number of times, they said.

A mayoral spokesman said the painting was paid for with private funds and did not reveal its cost.